This application claims priority to GB Application No. 9929800.2 filed Dec. 17, 1999.
The invention which is the subject of this application relates to a device and apparatus for use in the dissipation of heat which is generated by components within electrical apparatus when the apparatus is in operation.
The generation of heat by components such as integrated circuits when electrical apparatus is in operation is a well known problem and as a result many forms of apparatus include fans or other powered devices which are operated when the electrical apparatus is powered, to attempt to cool the components within the electrical apparatus housing. When one considers that it is believed that the life span of the components can be doubled for every 10 degree Celsius drop in operating temperature which can be achieved it will be appreciated that the temperatures in which the components operate is an important factor in product reliability. However a problem with the use of powered fans and the like to cool the air around the components is that they generate a noise which in some apparatus such as for example, broadcast data receivers for use with televisions, is unacceptable as it affects the use of the apparatus. The use of thermally conductive material is also well known wherein said material is applied to the inside surface of the housing in an attempt to provide some reduction in temperature by using the material to fill in air gaps in the housing but this material is expensive and can add considerably to the cost of the apparatus and as a result use of this form of material is still somewhat limited.
The aim of the present invention is to allow the use of thermally conductive material to provide an effective cooling effect on components within a housing of electrical apparatus and to do so in an economical manner which minimises the amount of the material which is required to be incorporated while maximising the effect of the same.
In a first aspect of the invention there is provided electrical apparatus which comprises at least one electrical or electronic component mounted within a housing, said component mounted on a first side of a printed circuit board and powered by an electricity supply when operational and, when powered, generates heat, said apparatus including thermally conductive material mounted therein to dissipate the heat generated and characterised in that said material is mounted on a raised platform mounted or on or formed by the housing in order to position the material on or adjacent the opposing side of the printed circuit board at the most efficient location to reduce heat with respect to the said component.
Preferably the component is on an upper surface of the printed circuit board and the thermally conductive material is on a lower surface.
Further preferably the thermally conductive material does not contact the component itself.
More typically the apparatus will comprise a series of components and if one thermally conductive material position is provided, that position will be determined with respect to design, heat generation and/or efficiency considerations. Alternatively, a number of locations can be provided, again, said location determined with reference to the area in which the heat is generated and/or the component locations.
In one embodiment the housing is formed of sheet material and said sheet material is formed into a platform or platforms at a designated location or locations with respect to the position of components within the housing. In one preferred embodiment the platform is formed so as to protrude upwardly from the surface of the housing which in normal use forms the base of the electrical apparatus and this allows the material to be positioned under the component or components at a required distance from the same.
In one embodiment the sheet material of the housing is sheet metal and the platform which is formed is frustoconical in shape and preferably has a series of slots formed at spaced intervals, said slots allowing two advantages, firstly the reduction in stresses on the sheet material caused by the formation of the platform and secondly the provision of air flow from externally of the housing into the same to improve the cooling effect.
Preferably solder resist material normally coated on a part or whole of the electrical apparatus and/or at least one electrical or electronic component is removed and/or not applied in the area of the thermally conductive material, such that solder is picked up in the area during the solder wave process. The extra solder on or surrounding the thermally conductive material increases the thermal conductivity and improves the Electro Magnetic Compatibility (EMC) performance in high current/high speed regions of the electrical apparatus and/or components.
In an alternative embodiment if the sheet material is a moulded plastic material then the platform can be formed as part of the mould process.
Preferably the thermally conductive material is a gel pad.
In a further aspect of the invention there is provided a method of providing a cooling effect on a component or components mounted on an upper surface of a printed circuit board within a housing of electrical apparatus, said method including the steps of identifying from tests the heat generated by the components when in operation, identifying the hottest areas within the housing and forming in the housing or locating thereon a platform upon which is mounted thermally conductive sheet material and said platform is of a size so as to position the thermally conductive material at or adjacent the underside of the printed circuit board at or adjacent to the hottest area so as to maximise the cooling effect of the material but without contacting the component or components.
The provision of the platform allows the use of a minimum of thermally conductive material, preferably provided in a sheet form, to maximum effect as the material can be positioned at the hottest areas in the housing rather than either being placed on the conventional housing inner surface which is removed from the hottest areas or alternatively the sheet material being provided in a relatively thick block to enable the same to reach the hottest areas which is prohibitively expensive.